Tags: #ASTM #buildingmaterials #buildingproducts #buildingscience #coatings #materialsscience #roguetesting
If it walks like a duck, swims like a duck, and quacks like a duck…. then it’s probably not a water resistive barrier.
Differentiating integral and integrated WRB panels was a major part of my recent presentation at the Greater Detroit Building Enclosure Council. I did so by definition but also by demonstration. One of the examples I provided was a gypsum-based integral WRB panel. It looks and feels like a conventional exterior grade gypsum panel. It also performs similarly when subjected to short-term ponding.
There are subtle differences that allow it to pass the low-bar standards of ASTM E331. These largely pertain to the facer and gypsum core interface. But that’s where it ends. Meeting the letter of the code (i.e. ASTM E331) does not mean it meets the intent of the code, which is very clear on this matter. The WRB must: 1) resist liquid water (by definition), 2) prevent water accumulation within the assembly (section 1402.2), and 3) provide a continuous barrier (section 1403.3).
Here, we see that after five hours, moisture content of the integral panel exceeds 5%. Three of the conventional sheathing panels resist water significantly better than the integral WRB. But the true intent of the code is expressed only by the integrated product, configured with a factory-applied coating.
Why do we try so hard only to get it so wrong? Because we don’t and therefore we do. Think differently. Test differently.